Discharger for electrophotographic copying apparatus

ABSTRACT

This specification discloses a discharger for use with an electrophotographic copying apparatus and removable with respect to the body of the copying apparatus. The discharger includes a single discharge wire or a plurality of discharge wires securely held by terminal receivers and extended therebetween. A shield member of substantially U-shaped cross-section surrounds the discharge wire or wires by three sides thereof. At least one side portion of the shield member is separate from the other two sides and secured to the body of the copying apparatus.

United States Patent Miyamoto Mar. 18, 1975' DISCHARGER FOR 3,348,041 10/1967 Rosenthal 250/32 4 YIN 3,358,289 12/1967 Polee 250/325 Egggfiggg COP G 3,499,143 3/1970 Martin 1 250/324 3,620,617 11/1971 Kelly et al 250/325 inventor: Kuichi Miyamoto, Tokyo, Japan Canon Kabushiki Kaisha, Tokyo, Japan Feb. 15, 1973 Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Feb. 21, 1972 Japan 47-2l264 References Cited UNITED STATES PATENTS 10/1957 Hayford et a1 250/324 4/1966 Gundlach 250/324 Primary E.ran1iner.lames W. Lawrence AssistaqtfixamineF- B. C. Anderson Attorney, Agent, or FirmFitzpatrick, Cella, Harper & Scinto [57] ABSTRACT This specification discloses a discharger for use with an electrophotographic copying apparatus and removable with respect to the body of the copying apparatus. The discharger includes a single discharge wire or a plurality of discharge wires securely held by terminal receivers and extended therebetween. A shield member of substantially U-shaped cross-section surrounds the discharge wire or wires by three sides thereof. At least one side portion of the shield member is separate from the other two sides and secured to the body of the copying apparatus.

3 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a discharger for use with an electrophotographic copying apparatus, and more particularly to an improved discharger which can provide a predetermined uniform intensity of discharge.

2. Description of the Prior Art The dischargers used with an electrophotographic copying apparatus generally comprise a very thin discharge wire extended between two support members and surrounded by a U-shaped or three-sided shield member of conductive material. When a high voltage is applied to the discharge wire for discharging, the wire tends to attract thereto various particles such as dust, toner particles and splashes of developing liquid present within the apparatus and such particles would thickly build up on the discharge wire during a longtime use of the apparatus. The build-up of particles would reduce or make irregular the discharging effect of the discharge wire, which in turn would result in the formation of disturbed copy images or other inconveniences. It is therefore required to change or clear the discharge wire at suitable time intervals of use.

However, the shield member forms an obstruction to the cleaning of the discharge wire, and it is difficult to clean it through the opening and more difficulties are encountered especially in satisfactorily cleaning smallsized dischargers such as discharger for squeezing developing liquid and discharger used for image transfer.

In addition, much skill is required to change the discharge wire because it must be extended always at a predetermined position.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-noted disadvantages and to provide an improved discharger for use with an electrophotographic copying apparatus and which can be removably mounted with respect to the body of the copying apparatus so as to permit cleaning of a discharge wire to be carried out readily and simply if required.

It is another object of the present invention to provide an improved discharger for use with an electrophotographic copying apparatus and which employs a plurality of discharge wires replaceable with one another for discharging so as to economize the time and cost required for the cleaning of the discharge wires.

To achieve these objects, the discharger of the present invention may comprise a discharge wire held by terminal receivers, and a shield member of substantially U-shaped cross-section surrounding said discharge wire by three sides thereof. At least one side portion of the shield member may be secured to the body of the copying apparatus. In another embodiment of the present invention, the discharger employs a plu- BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more fully apparent from the following detailed description thereof takenin conjunction with the accompanying drawings, in which:.

rality of discharge wires provided so that a high voltage may be applied to only one of these discharge wires for effecting discharge with no voltage being applied to the other discharge wires. These discharge wires are replaceable with one another for discharging, and they are secured to rotatable turret means so as to be interchangeably usable.

FIG. 1 is a side elevation of a copying apparatus to which the present invention is'applicable;

FIG. 2 is a cross-sectional view showing an embodiment of the present invention;

FIG. 3 is a cross-sectional view showing another embodiment of the present invention; and

FIG. 4 is a longitudinal section of the FIG. 3 embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Description will first be made of an example of the electrophotographic copying apparatus to which the present invention is applied.

Referring to FIG. 1, a drum 1 is rotatable in the direction of arrow and securely carries thereover a photosensitive medium 2 which comprises a dielectric or insulating layer, a photoconductive layer and a conductive layer. The drum 1 is surrounded by a primary discharger 3, a secondary discharger for simultaneous application of light and charge of the polarity opposite to that of the primary discharger or an AC discharger 4, and an overall exposure device 5. An electrostatic latent image may be formed on the photosensitive medium by such electrophotographic processes as disclosed in applicants Japanese Patent Publications Nos. 23910/1967 and 24748/l968. The latent image so formed may then be visualized by adeveloping device 6, whereafter any excess developing liquid on the photosensitive medium may be squeezed away by a squeeze discharger 7. On the other hand, a sheet of copy paper P may be delivered from a cassette C toward the photosensitive medium 2 by means of a paper feed roller 8 and a pair of transport rollers 9. The copy sheet may be brought into intimate contact with the visualized image with one end thereof bearing against a separator belt 11 extending at one side of the drum, so that the visualized image may be transferred to the copy sheet as the latter is charged from the back side thereof by a transfer discharger 10. Subsequently, the copy sheet P may be separated from the surface of the photosensitive medium 2 by separator belt 11 and roller 12 and with the aid of an air blast from a duct 13, whereafter the copy sheet is directed onto a heat-fixing plate 14. After the transferred image is fixed, the copy sheet may pass through a first pair of discharge rollers 15 so as to have any residual charge on the copy sheet removed therefrom, and further pass through a second pair of discharge rollers 17 and finally discharge onto a tray 18. In the meantime, the residual image on the surface of the photosensitive medium 2 may be cleared away by blades 19 and 20 so as to make the photosensitive medium 2 ready for a subsequent copy cycle.

FIG. 2 shows an embodiment of the present invention which is applicable as any of the primary discharger, squeeze discharger and transfer discharger and the like used, for example in the above-described copying apparatus.

As shown in FIG. 2, the discharger of the present invention has three side plates 21, 22 and 23, one of which 21 is separate from the other two and secured to a portion of the apparatus body while the other two side plates 22 and 23 are formed into an L-shape and secured to terminal receivers 24, 24 disposed at the op posite ends of the length of a discharge wire 27. A slide block 25 is attached to the underside of the bottom plate 23 and supported by a guide rail 26 underlying the separate side plate 21 so as to provide a removable construction of the discharging means.

Thus, when the slide block 25 is fitted into the guide rail 26 and the discharging means is mounted to the apparatus body, the three sides 21-23 will provide a shield member and if required, the discharging means may be withdrawn out of the apparatus body to permit ready access to the discharge wire 27 in two directions, i.e. from above and from one side thereof, thus ensuring the discharge wire to be positively cleaned.

In the above-described embodiment, it will be apparent that two of the side plates 21 and 22 may be secured to the apparatus body.

The means for overcoming the contamination of the discharge wire to provide a predetermined uniform intensity of discharge may be accomplished by replacement of the discharge wire'as well as by the abovedescribed cleaning method. The replacement method is meritorious in that it requires no cleaner means which tends to stain the human hands or the like, but instead, this method requires minute cares to be taken in handling the discharge wire which is so thin and delicate, thus making it nearly impossible for any layman to carry out the replacement of such discharge wire. This in turn necessitates frequent visits of service engineers or the like to the user, and accordingly leads to a huge maintenance cost incurred on the part of the user.

The present invention also provides a discharger in which the discharge wire may readily and easily be replaced by the hands of anybody.

FIGS. 3 and 4 show another embodiment of the discharger according to the present invention. The discharger of this embodiment comprises three discharge wires 27,, 27 and 27;; extended between turrets 30 and 31 provided on terminal receivers 28 and 29 forming the opposite ends of the discharger. One of the three wires 27, is located on the center line of the discharger and the other two wires 27, and 27,, extend adjacent to a shield member 32. Rotation of operating dials 30, and 31, for the turrets 30 and 31 will cause the discharge wires 27, and 27;, to replace each other in position. A high voltage supplied from a high voltage source to a connector pin 33 will pass through a contact 34 and a terminal 35, and only to the central discharge wire 27,

' 4 to effect dicharge. At this time, no voltage is applied to the other two discharge wires 27 and 27 which, being located near theshield member 32, will affect in no way the corona discharge from the central discharge wire 27,.

If such discharger is used until the'central discharge wire 27, is too much contaminated for further use, the dials 30, and 31, forthe turrets 30 and 31 may be r0- tated for 120 respectively to thereby displace the contaminated discharge wire 27, toward the shield member 32 while causing theclean or uncontaminated discharge wire 27, to assume the center position ready to effect normal corona discharge. Since the discharge wires are all tensioned by springs 36,, 36 and 36 the two dials 30, and 31 need not be actuated simulta-- neously with each other. Thus, the discharger is simple to construct and handle.

As has been described hitherto, the present invention employs a plurality of discharge wires which are replaceable with one another readily and simply by any layman. This is highly useful to greatly reduce the frequency. of wire change by a technician or service engineer and also to reduce the maintenance cost incurred.

Although the illustrated embodiment has been shown to employ three discharge wires, it will be apparent that any greater number of wires may be used as desired. In these cases, however, the discharge wires must be located so as not to affect each other during discharging because an adverse effect would occur if any one of them were located extremely adjacent to another discharge wire.

I claim:

1. A discharger for use with an electrophotographic copying apparatus comprising a plurality of discharge wires, means for interchanging said discharge wires with one another for discharging, terminal receivers for holding said discharge wires, a shield member surrounding said discharge wires on three sides thereof, at

least one side portion of said shield member being secured to the body of the said copying apparatus and the remaining portion of the discharger being removable with respect to the body of said copying apparatus.

2. A discharger according to claim 1, wherein, means are provided for applying a high voltage to at least one of said discharge wires for effecting discharge while no voltage is applied to the other discharge wires.

3. A discharger according to claim 2, wherein said discharge wires are secured to rotatable turret means so as to be interchangeably used.

UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No, 318721307 Dated March 18, 1975 KOICHI MIYAMO'I'O Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title Page, "KUICHI MIYAMOTO" should read -KOICHI MIYAMOTO;

Column 4, line 1, "dicharge" should read -discharge-.

Signed and sealed this 24th day of June 1975.

(SEAL) Attest:

C I--'IARSI-ZALL DANN RUTH C nAQOD-I Commissioner of Patents Attestlng Officer and Trademarks QM PO-10S0 (10-69) USCOMM-DC flO376-P69 U.S. GOVERNMENT PRINTING OFFICE i989 0-366-3Jl, 

1. A dischargeR for use with an electrophotographic copying apparatus comprising a plurality of discharge wires, means for interchanging said discharge wires with one another for discharging, terminal receivers for holding said discharge wires, a shield member surrounding said discharge wires on three sides thereof, at least one side portion of said shield member being secured to the body of the said copying apparatus and the remaining portion of the discharger being removable with respect to the body of said copying apparatus.
 2. A discharger according to claim 1, wherein, means are provided for applying a high voltage to at least one of said discharge wires for effecting discharge while no voltage is applied to the other discharge wires.
 3. A discharger according to claim 2, wherein said discharge wires are secured to rotatable turret means so as to be interchangeably used. 